clearfix::before,clearfix::after{
    content: '';
    display : table ;
    clear: both ; 
}
.top{
    width: 100%;
    height: 140px;
}
body{
   font: 14px/1.5 Helvetica Neue,Helvetica,Arial,Microsoft Yahei,Hiragino Sans GB,Heiti SC,WenQuanYi Micro Hei,sans-serif
}
